No, I mean
selective outlining. It's a method used in pixel art that partly makes outlines look better (sort of like anti aliassing) but more importantly so that your outlines don't disappear completely against a background consisting of the same color as your outline. It helps keep your sprites visually distinct from the background at all times.
It's a minor critique, really, and it may not fit your style or you may want to omit it because it's extra work, but I tend to consider it one of the more important things to do on sprites because when your sprites are clearly visually distinct from the background it makes it easier/less tiresome to play.
I like the attention to detail.